The preferred technology for many late-model vehicle engines is multi-layer steel (MLS). Recognizing that replacement applications typically offer less-than-ideal sealing conditions, Federal-Mogul engineers created an MLS technology that addresses the true aftermarket repair environment. The result is the Fel-Pro® line of PermaTorqueMLS products. PermaTorqueMLS head gaskets offer a wide range of benefits, including: Strategically placed sealing beads that help eliminate leak paths Extra-strong stopper layers that provide superior primary combustion sealing (where applicable) Full-hard stainless steel material that maintains its shape despite thermal expansion and scrubbing between the block and head a unique, application-specific coating that enhances sealabilityWhat's more, Fel-Pro PermaTorqueMLS head gaskets provide the torque retention required to maintain positive contact pressure between head and block over the life of the repair. MLS technology is specified on most current U. S. , European and Asian engines in production.Pit Stop USA offers Fel-Pro Perma Torque MLS Head Gasket (1) - 4.200" Bore - .040" Compressed Thickness - SB Chevy 1144 at low everyday prices. Be sure to check out all of our products from Fel-Pro Performance Gaskets including Fel-Pro Performance Gaskets Cylinder Head Gaskets - Small Block Chevy.